Non-terminating double containment fitting

ABSTRACT

A double containment fitting for connection to a double containment tubing system with an outer, secondary containment tubing surrounding an inner, primary tubing. The fitting includes a fitting body defining a central passageway, the fitting body having a center portion disposed between opposed first and second body ports. The fitting body is configured to receive the tubing system into the first body port. The central passageway has a diameter in the first port selected to allow the secondary tubing into the first body port. A connection system mechanically secures the secondary tubing to the first body port.

BACKGROUND

Double containment piping or tubing systems are commonly used totransport fluids in various environments. A common application is thatof transport of hazardous materials, such as in processes utilizinghazardous materials. One exemplary application is that of semiconductorfabrication processes, utilizing chemicals of a hazardousclassification, although there are many other applications using doublecontainment systems. A double containment system utilizes an outer,secondary containment pipe or tubing surrounding an inner, primary pipeor tubing, with an annulus or interstitial space between the inner andouter pipes or tubing. In the event of a leak from the inner tubing, theouter tubing contains the fluid.

Even though the outer tubing of a double containment system containsfluid leaking from a primary inner tubing, the fluid within theinterstitial space presents a problem of handling the leaked fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of the disclosure will readily be appreciated bypersons skilled in the art from the following detailed description whenread in conjunction with the drawing wherein:

FIG. 1 is a schematic diagram illustrating an exemplary environment inwhich one or more non-terminating double containment fittings may beused.

FIG. 2 is an isometric view of an exemplary embodiment of anon-terminating double containment fitting.

FIG. 3 is a front view of the exemplary fitting of FIG. 2. FIG. 3A is across-sectional view taken along line 3A-3A of FIG. 3.

FIG. 4 is a cross-sectional view of the unitary body structure of thefitting of FIG. 2.

FIG. 5 is an exploded view of the exemplary fitting of FIG. 2. FIG. 5Ais an exploded view of a nut and sleeve of the fitting of FIG. 2. FIG.5B is a cross-sectional view of the nut and sleeve assembled together.

FIG. 6 is an isometric view of an alternate embodiment of anon-terminating double containment fitting.

FIG. 7 is an isometric view of the fitting of FIG. 6 with the nutdisengaged. FIG. 7A is an isometric view of the fitting of FIG. 6 withthe nut and sleeve in exploded view.

FIG. 8 is a cross-sectional view of the fitting of FIG. 6.

DETAILED DESCRIPTION

In the following detailed description and in the several figures of thedrawing, like elements are identified with like reference numerals. Thefigures may not be to scale, and relative feature sizes may beexaggerated for illustrative purposes.

An exemplary operating environment 10 for a non-terminating doublecontainment fitting is illustrated in FIG. 1. A tool 12 uses a fluid,e.g. a liquid chemical in performing some process task at a point ofuse. The point of use may include, for example, a tool used insemiconductor fabrication or pharmaceutical manufacture. A container 14holds a supply of the fluid in its reservoir 16. The fluid is typicallya hazardous material. Examples of the hazardous materials includecaustic fluids, such as nitric acid, hydrochloric acid, sulfuric acid,hydroxides, ammonia and other chemical formulations. The container 14 isconnected to the point of use 12 by a double containment tubing system20, which includes a primary process tube 22 and an outer, secondarytube 24. The tubes may be of various diameters, depending on theapplication. For example, tube sizes of ¼-½ inch, ⅜-¾ inch, ½-¾ inch,½-1 inch, ¾-1 inch, and 1-1¼ inch, are outer diameter pair sizes for theprimary process line or tube and the secondary containment line or tube.Other sizes may be used, depending on the application.

In an exemplary operating environment, the primary and secondary linesmay be flexible tubing, for example, tubing fabricated ofPerFluoroAlkoxy (PFA) and TetraFluorEthylene-Perfluorpropylene (FEP).

A pump 18 is typically mounted in the container 14 to pump the fluidfrom the container 14 through the tubing system 20 to the point of use12. The double containment system 20 addresses the possible situation inwhich the fluid leaks from the primary tube 22, with the outer tubecontaining the leaking fluid and preventing the fluid from leakingoutside the system 20.

The system 20 is connected to the point of use 12 by a terminatingdouble containment fitting 30 or a non-terminating fitting 100. Aterminating double containment fitting is a fitting which passes theprimary tube through to an operating fitting or port at the point ofuse, while terminating or closing the space between the primary andsecondary tubes. Thus, in the event of a leak, the fluid contained inthe annular space between the primary and secondary tubes does not passthrough the fitting 30. In the alternative, the fitting may be anon-terminating fitting 100, which passes both the primary and secondarytubes through the fitting. An exemplary embodiment of fitting 100 isdescribed below with respect to FIGS. 6-8.

In this exemplary embodiment, the system 20 is connected to thecontainer 14 by a non-terminating double containment fitting 100. Thefitting may be supported by a wall or bulkhead of the container 14. Thesystem 20 is passed through the fitting 100 to the interior of thecontainer, to a bypass non-terminating fitting 50, and the primarytubing 22 is connected to the pump 18. In other applications, thefitting 50 within the container 14 may be eliminated. A fitting 50 mayalso optionally be employed at the point of use 12, as diagrammaticallyillustrated in FIG. 1, in phantom.

The fitting 50 provides a liquid path for liquid leaked from the primarytube 22 and captured within the annular space between the primary andsecondary tubes 22, 24 to be passed out of the system 20, e.g. back tothe container reservoir 14 or to another container or disposition. Anexemplary embodiment of the fitting 50 is illustrated in FIGS. 2, 3, 3A,4, 5, 5A and 5B. The fitting 50 is a generally T-shaped assembly. Afitting body 52 is formed as a unitary one-piece structure, typically byinjection-molding, fabricated from PFA in this exemplary embodiment. Thebody 52 defines a central passageway 60 and a bypass passageway 62perpendicular to the central passageway (FIG. 4). The body 52 has acenter portion 52A, disposed between opposed first and second body ports52B and 52C. The tubing system 20 from the tool enters the fittingthrough port 52B, and the primary tubing 22 is passed through thefitting and out the port 52C. The secondary tubing 24 is terminated inthe first body port 52B at shoulder surface 56B1A (FIGS. 3A, 4). Asdescribed more fully below, in this exemplary embodiment, a connectionsystem is provided for each of the first and second ports to secure theouter tubing 24 at the fitting port 52B.

The first body port 52B includes a threaded portion 52B1, which isengaged by a nut 56A. The port 52B further includes a shoulder portion52B2 and a tapered portion 52B3, which terminates at a distal end 52B4,having a beveled tip surface 52B4-1 (FIG. 4). A separate sleevestructure 54A is fitted within the nut 56A. The sleeve 54A has a solidconfiguration, and is free of longitudinal slots. The sleeve 54A has aninner diameter at its interior end which is slightly larger than theouter diameter of the tip 52B4 of the tapered portion 52B3, but which isslightly smaller than the outer diameter of the tapered portion 52B3adjacent the shoulder portion 52B2. The nut 56A is fabricated fromPolyvinylidene Fluoride (PVDF), and the sleeve 54A is fabricated fromPFA, in this example. The opening diameter of the tapered portion 52B3is selected to be slightly larger than the outer diameter of thesecondary tubing 24, so that the tubing system 20 can be insertedthrough the tapered portion and into the body 52, with the nut 56A andsleeve 54A in an unthreaded, untightened position relative to thefitting body. The end of secondary tubing 24 is positioned against thestop shoulder 52B1A of the first body port, i. e. terminated against,shoulder 52B1A.

FIGS. 5A and 5B illustrate an exemplary nut and sleeve, nut 56A andsleeve 54A. The sleeve and nut are each of a unitary, one-piececonstruction in this exemplary embodiment. The sleeve is structured foran interference fit into the nut, as illustrated in FIG. 5B. The outerdiameter of the end 54A-1 of the sleeve is slightly larger than theinner diameter of the nut opening at the nut end 56A-1, and the roundededge of the end 54A-1 facilitates the press fit of the sleeve intoengagement with the nut. The sleeve is formed with a groove 54A-2 inwhich inner lip portion 56A-2 is seated in the engaged position.Typically, the sleeve may be assembled to the nut at the factory, to theassembled condition illustrated in FIG. 5B. The sleeve 54A is fabricatedof a softer, more flexible material (such as PFA) than that of the nut(which may be PVDF), facilitating the assembly of the sleeve into thenut.

The nut 56A is tightened on the threaded portion 52B1 of the fittingbody 52, to the position illustrated in FIG. 3A, drawing the sleeve 54Aalong the outer surface of the tapered portion 52B3 until stoppedagainst shoulder portion 52B2, and compressing the tapered portion 52B3into contact with the outer surface of the secondary tubing 24. Thesleeve 54A has an internal angled shoulder surface which stops againstthe corresponding beveled tip surface (surface 52B4-1, FIG. 4). In oneexemplary embodiment, the outer diameter (OD) of the primary tubing 22is 0.50 inch, the inner diameter (ID) of the tubing 22 is 0.38 inch,with corresponding dimensions of the secondary tubing 24 as 0.75 inch ODand 0.63 inch ID. This provides a difference of 0.13 inch between the ODand ID of the primary and second tubings 22, 24.

The threaded portion 52B1, tapered portion 52B3, sleeve 54A and nut 56Acooperate to form an annular mechanical smear seal or smear connectionof the fitting body 52 to the secondary tubing 24 at the first port 52B,in the annular region underlying the tapered portion 52B3 of the fittingbody. The smear seal mechanically secures the outer tubing 24 in placewithin the fitting body, to prevent the tubing from being pulled out ofthe fitting or pushed through the fitting, while the nut is in place. Inan exemplary embodiment, the smear seal extends along a substantiallength of the tapered portion, e.g. on the order of ½ inch to ¾ inch inan exemplary embodiment, and results from three to four revolutions ofthe nut on the threaded portion 52B1 of the fitting body. As usedherein, a smear seal or smear connection occurs when similar materialsare under a compression force from a harder, more rigid material. Inthis example, the nut 56A is formed of a harder, more rigid materialthan that of the sleeve 54A, the fitting body 52 and the outer tubing24. As the nut is threaded onto the fitting body, the sleeve compressesthe tapered portion 52B3, in turn compressing the fitting body onto theouter tubing 24, resulting in a smear seal between the tubing and thefitting body. The smear seal contrasts with a conventional compressionseal, which typically results in a compression at an annular bead, witha relatively short longitudinal seal length. The conventionalcompression seal also tends to deform the sealed components, typicallypermanently, at the seal junction. In contrast, with the smear seal orseal connection, in an exemplary embodiment, the nut 56A and sleeve 54Acan be removed from the fitting body, to permit disassembly of thefitting from the tubing system 20, without permanently deforming thetubing 24.

The primary tubing 22 is passed through the fitting 50, extending fromthe second body port 52C, and in this exemplary embodiment, is connectedto a pump in the supply container 14. The second body port 52C includesa threaded portion 52C1, which is engaged by a nut 56B. The port 52Cfurther includes a shoulder portion 52C2, and tapered portion 52C3,which terminates at a distal end 52C4. A separate sleeve 54B is fittedwithin the nut 56B. The nut 56B is fabricated of PVDF, and the sleeve54B from PFA, in this example. The sleeve 54B, nut 56B and the taperedportion 52C3 of the fitting body 52 cooperate in the same manner asdescribed above regarding the first port. The opening diameter of thetapered portion 52C3 is selected to be slightly larger than the outerdiameter of the primary tubing 22, so that the tubing 22 can be insertedthrough the tapered portion and out the body 52. The nut 56B istightened on the threaded portion 52C1, to the position illustrated inFIG. 3A, drawing the sleeve 54B along the outer surface of the taperedportion until stopped at shoulder portion 52C2, and compressing thetapered portion into sealing contact with the outer surface of theprimary tubing 22. The threaded portion 52C1, tapered portion 52C3,sleeve 54B and nut 56B cooperate to form a mechanical smear seal orsmear connection between the tapered portion 52C3 of the fitting bodyand the primary tubing 22 at the second port 52B. The nut 56B withsleeve 54B can be removed, to permit disassembly of the fitting from thetubing system 20.

The tubing system 20 provides an annular space 26 between the primarytubing 22 and the outer, secondary tubing 24. Even though the secondarytubing 24 is terminated at shoulder 52B2, the fitting 50 maintains anannular space 26A (FIG. 3A) through the center fitting portion 52Abetween the primary tubing 22 and the cylindrical surface 52A1 of theportion 52. Thus, any fluid leaking from the primary tubing 22 in thesystem 20 may flow into the annular space 26A. The threaded portion 52C1of the second port 52C includes an internal tapered surface 52C1-A whichat its junction with the tapered portion 52C4 closes the annular space26A. Thus, any fluid in the annular space 26A cannot escape through theport 52C.

In this embodiment of a non-terminating fitting 50, a bypass port 52D isprovided, which is in fluid communication with the annular space 26A,and allows fluid in the annular space to flow out through the port 52D.The bypass port includes a threaded portion 52D1, which is engaged by anut 56C. The port 52D further includes a tube engaging portion 52D2,which terminates at a beveled distal end 52D3. A bypass passageway 62 isdefined through the port 52D, in communication with the annular spaced26A when the tubing 22 is in place within the fitting 50. The nut 56C isfabricated of PVDF, in this example. A flared end 60A of an overflowtube 60 is fitted over the tube engaging portion 52D2. The nut 56C istightened on the threaded portion 52D1, to the position illustrated inFIG. 3A, compressing the flared end portion 60A between the tubeengaging portion 52D3 and the nut, to provide a leak proof seal.

The overflow tubing 60 may be connected to the reservoir 16 to replenishthe volume of source fluid. Alternatively, the overflow tubing may beconnected to a separate overflow container, or to another destination.

An alternate embodiment of a non-terminating double containment fitting100 is illustrated in FIGS. 6-8. In this embodiment, both the primarytubing 22 and the secondary tubing 24 are passed through the fitting.The secondary fitting may terminate between the fitting and the pump,for example. This fitting can be used in applications in which theleaked fluid in the annular space 26 can drain back into the supplycontainer 14, for example, by cutting or ending the secondary tubing 24upstream of the pump. In this embodiment, the fitting 100 includes afitting body structure 102 having an opening 102D defined through thebody, a threaded nut 104 and sleeve 104. Alternatively, a fitting 50 canbe used with the fitting 100, e.g. at the point of use as illustrated inphantom in FIG. 1.

A center portion 102A of the body structure defines a flange. A firstthreaded end body portion 102B extends from one side 102A1 of the flangeor center portion, and is configured to receive the double containmentsystem 20 from the tool.

The body portion 102 further defines a second threaded end body portion102C extending from an opposite side 102A2 of the flange portion. Thebody portion 102C includes an externally threaded portion 102C1,configured for engagement with the internal threads of the nut 104. Thebody portion 102C further includes a shoulder portion 102C2 and atapered portion 102C3 with tip 102C4, extending away from the flangeportion 102C1.

The opening 102D in the body structure 102 has a first diameter D1 inthe first threaded end portion 102B and in the center, flange portion102A, which is larger (by 0.13 inch in an exemplary embodiment with theforegoing exemplary dimensions of the primary and secondary tubings)than the outer dimension of the secondary tubing 24, so that thesecondary tubing, with primary tubing 22, can be easily fitted into thefirst end portion. The surface 102C1-A of the center opening 102D tapersdown to a reduced opening diameter D2 within portion 102C1 of the secondportion 102C. Diameter D2 is just slightly larger than the outerdiameter of secondary tubing 24, so that the tubing 24 can be fittedthrough the end portion 102C. Exemplary dimensions for D1, D2 are 0.88inch and 0.76 inch, respectively, for the example of the secondarytubing OD of 0.75 inch

The sleeve 104, nut 106 and the tapered portion 102C3 with tip 102C4 arecooperatively dimensioned so that, as the nut 106 is tightened on thethreaded portion 102C1, to the position illustrated in FIG. 8, drawingthe sleeve 104 along the outer surface of the tapered portion untilstopped at shoulder portion 102C2, and compressing the tapered portioninto frictional contact with the outer surface of the primary tubing 22,forming a mechanical smear seal, or smear connection, in the same manneras described above with respect to nut 56A, sleeve 54A, tapered portion52B3 and tubing 24. The nut 106 with sleeve 104 can be removed from thefitting body 102 to allow the tubing system to be withdrawn from thefitting, or repositioned along its longitudinal length

The fitting 100 may be secured in a bulkhead opening, with a nut (notshown in FIG. 8) threaded onto the threaded portion 102B1 to sandwichthe bulkhead between the flange surface 102A1 and the nut.

Although the foregoing has been a description and illustration ofspecific embodiments of the subject matter, various modifications andchanges thereto can be made by persons skilled in the art withoutdeparting from the scope and spirit of the invention.

What is claimed is:
 1. A double containment fitting for connection to adouble containment tubing system with an outer, secondary containmenttubing surrounding an inner, primary tubing, with an annular spacebetween the inner and outer tubing, the fitting comprising: a fittingbody defining a central passageway, the fitting body having a centerportion disposed between opposed first and second body ports; thefitting body configured to receive the tubing system within the firstbody port; the central passageway having a first diameter in the firstport selected to allow the secondary tubing into the first body port; aconnection system for mechanically securing the secondary tubing to thefirst body port, the system comprising: a first external threadedsurface on a first portion of the first body port; a tapered portion ofthe first body portion extending from the first portion and surroundingthe central passageway, the tapered portion having a first thicknesswhich tapers from a first thickness adjacent the first external threadedsurface to a reduced thickness adjacent a tip of the first port; athreaded nut having internal threads and configured to engage theexternal threaded surface on the first body port; a sleeve configured tofit within the threaded nut and over the tapered portion, and to apply acompression force on the tapered portion of the first body port as thenut is threaded onto the external threaded surface to compress thetapered portion onto an outer surface of the secondary tubing to form anannular mechanical smear seal connection between an internal surface ofthe tapered portion and the outer surface of the outer, secondary tubingto fix the outer, secondary tubing in place within the fitting body; andwherein the nut is made of a material which is harder than the materialor materials from which the sleeve, the fitting body and the tubing arefabricated.
 2. The fitting of claim 1, wherein the fitting body is aunitary one-piece structure fabricated from a plastic material.
 3. Thefitting of claim 1, wherein the secondary tubing terminates within thefitting body in said central passageway.
 4. The fitting of claim 3,wherein the fitting body includes a stop shoulder for registering aposition of an end of the secondary tubing.
 5. The fitting of claim 1,wherein the nut is a unitary one-piece structure fabricated from aplastic material, and the sleeve is a unitary structure fabricated froma different plastic material than the nut.
 6. The fitting of claim 5,wherein the nut is fabricated from Polyvinylidene Fluoride (PVDF), andthe sleeve and the fitting body are fabricated from PerFluoroAlkoxy(PFA) or TetraFluorEthylene-Perfluorpropylene (FEP).
 7. The fitting ofclaim 1 wherein the connection system is configured to free thesecondary tubing from engagement with the fitting body by disengagementof the nut from the fitting body.
 8. A double containment fitting forconnection to a double containment tubing system with an outer,secondary containment tubing surrounding an inner, primary tubing, withan annular space between the inner and outer tubing, the fittingcomprising: a fitting body defining a central passageway, the fittingbody having a center portion disposed between opposed first and secondbody ports; the fitting body configured to receive the tubing systemwithin the first body port; the central passageway having a firstdiameter in the first port selected to allow the secondary tubing intothe first body port; a connection system for mechanically securing thesecondary tubing to the first body port, the system comprising: a firstexternal threaded surface on a first portion of the first body port; atapered portion of the first body portion extending from the firstportion and surrounding the central passageway, the tapered portionhaving a first thickness which tapers from a first thickness adjacentthe first external threaded surface to a reduced thickness adjacent atip of the first port; a threaded nut having internal threads andconfigured to engage the external threaded surface on the first bodyport; a sleeve configured to fit within the threaded nut and over thetapered portion, and to apply a compression force on the tapered portionof the first body port as the nut is threaded onto the external threadedsurface to compress the tapered portion onto the secondary tubing toform a mechanical connection between an internal surface of the taperedportion and the outer, secondary tubing of the tubing system to fix theouter tubing in place within the fitting body; wherein the nut is madeof a material which is harder than the material or materials from whichthe sleeve, the fitting body and the tubing are fabricated; and whereinthe fitting body further defines a bypass passageway transverse to thecentral passageway, the fitting body having a bypass body port throughwhich the bypass passageway extends, the bypass passageway configured influid communication with the annular space between the primary andsecondary tubing within the fitting body, wherein fluid in the annularspace is conducted to the bypass body port.
 9. A double containmentfitting for connection to a double containment tubing system with anouter, secondary containment tubing surrounding an inner, primarytubing, with an annular space between the inner and outer tubing, thefitting comprising: a fitting body defining a central passageway, thefitting body having a center portion disposed between opposed first andsecond body ports; the fitting body configured to receive the tubingsystem within the first body port; the central passageway having a firstdiameter in the first port selected to allow the secondary tubing intothe first body port; a connection system for mechanically securing thesecondary tubing to the first body port, the system comprising: a firstexternal threaded surface on a first portion of the first body port; atapered portion of the first body portion extending from the firstportion and surrounding the central passageway, the tapered portionhaving a first thickness which tapers from a first thickness adjacentthe first external threaded surface to a reduced thickness adjacent atip of the first port; a threaded nut having internal threads andconfigured to engage the external threaded surface on the first bodyport; a sleeve configured to fit within the threaded nut and over thetapered portion, and to apply a compression force on the tapered portionof the first body port as the nut is threaded onto the external threadedsurface to compress the tapered portion onto the secondary tubing toform a mechanical connection between an internal surface of the taperedportion and the outer, secondary tubing of the tubing system to fix theouter tubing in place within the fitting body; wherein the nut is madeof a material which is harder than the material or materials from whichthe sleeve, the fitting body and the tubing are fabricated; and whereinthe sleeve has an angled internal surface, and said first port has abeveled tip, and wherein the angled internal surface of the sleeve isconfigured to contact the beveled tip of the first port as the nut isthreaded onto the external threaded surface of the first port.
 10. Adouble containment fitting for connection to a double containment tubingsystem with an outer, secondary containment tubing surrounding an inner,primary tubing, with an annular space between the inner and outer tubingthe fitting comprising: a fitting body defining a central passageway anda bypass passageway transverse to the central passageway, the fittingbody having a center portion disposed between opposed first and secondbody ports and a bypass body port through which the bypass passagewayextends; the fitting body configured to receive the tubing system intothe first body port, and to pass the primary tubing through the centralpassageway and out the second body port; the central passageway having afirst diameter in the first port selected to allow the secondary tubinginto the first body port, the central passageway having a seconddiameter in the second port and selected to be allow the primary tubingto pass through the second port, the first diameter larger than thesecond diameter; the bypass passageway configured in fluid communicationwith the annular space between the primary and secondary tubing withinthe fitting body, wherein fluid in the annular space is conducted to thebypass body port; a first connection system for mechanically securingthe secondary tubing to the first body port, and a second connectionsystem for mechanically sealing the primary tubing to the second bodyport; wherein the first connection system comprises: a first externalthreaded surface on a first portion of the first body port; a firsttapered portion of the first body port extending from the first portionand surrounding the central passageway; a first threaded nut havinginternal threads and configured to engage the first external threadedsurface on the first body port; a first sleeve configured to fit overthe first tapered portion and within the first threaded nut, and toapply a compression force on the first tapered portion of the first bodyport to compress the tapered portion onto the secondary tubing as thefirst threaded nut is threaded onto the first external threaded surface.11. The fitting of claim 10, wherein the second connection systemcomprises: a second external threaded surface on a first portion of thesecond body port; a second tapered portion of the second body portextending from the first portion of the second body port and surroundingthe central passageway; a second threaded nut having internal threadsand configured to engage the second external threaded surface on thesecond body port; a second sleeve configured to fit over the secondtapered portion and within the second threaded nut, and to apply acompression force on the second tapered portion of the second body portas the second nut is threaded onto the second external threaded surfaceto compress the second tapered portion onto the primary tubing.
 12. Thefitting of claim 10, wherein the secondary tubing terminates within thefitting body in said central passageway.
 13. The fitting of claim 12,wherein the fitting body includes a stop shoulder for registering aposition of an end of the secondary tubing.
 14. The fitting of claim 10,wherein the fitting body is a unitary one-piece structure fabricatedfrom a plastic material.
 15. The fitting of claim 10, wherein the bypassport includes a bypass port external threaded portion, the fittingfurther comprising a bypass port threaded nut configured to engage thebypass port and to secure a bypass tubing in place on the bypass port.